In ordinary cases countershaft is a very simple mechanism. In the oldest form of engine lathes all that was needed was a cone pulley identical with the spindle taper, and at the other end of the axis of a tight and loose pulley for driving pulley belt on the axis of the main line. Then, as threads requires backward movement of the lathe spindle, adding a second pair of pulleys and a transverse band applied for that purpose. The displacement of these belts was too slow for practical work and used claws. These were the old type "horn clutch" making substantial "noise" in their use and start working with too much shock.
Subsequently friction clutches or friction pulleys were prepared, and these in one form or another are largely
Until relatively recently the winch had only two was the standard forward speed, the other a significantly faster speed backward, which is mainly used in threading. From time to time, for special work, this speed "backup" was used by changing the transverse band of "open belt" and get another speed range. Surely this suggests the benefits of a regular two-speed counter shaft which has now become very common, as aconvenient and economical method of adding another set of gears for the lathe.
There are currently used in a number of popular lathes oriented intermediate shafts and various devices for producing a variable speed by a gradual increase or decrease the number of revolutions per minute. This result has been sought by a number of different devices with more or less success. Some of them have had good features to congratulate them, while others were more along the lines of the improvisations that perform the desired results very inefficiently, and ate too much of the nature of the "traps" as understood by the engineer, and So were relatively short-lived and unpopular.
Figure 147 shows an example of the intermediate shafts regular type lathe. Is made by the FE Reed Company, and comprises a cone pulley, a homolog of the cone of the spindle, and two friction pulleys mounted on the shaft, which is supported by two hangers having self-lubricating boxes . Friction pulleys consist of a suitable pulley, which rotates inside of the rim for receiving the friction of the band B, or blown with an edge protruding from the arms and over pulley inside for the same purpose, as shown in the drawing. The friction band B is divided into a point as shown, the two loose ends have projecting lugs in b, b, perforated by pivot bolts which are connected with levers C, C, whose ends are adjustably connected by screws and nuts shown at d
Figure 147 -. Countershaft friction winches, made by New Haven Company.Deslizante Manufacturing on shaft between the pulleys is the clutch collar E, whose horns E, E, are adapted to enter between the ends of the levers C, a /. These horns being wedge shaped will, when thrust between the free ends of the levers of C, C, they separate, and as a fulcrum its ends are connected, and by means of pivot pins attached to the free ends The B band friction tend to expand the opening of the band, enlarge its diameter to contact with the inner surface of the pulley (or the rim at the same address for that purpose), causing friction sufficient to transmit the requerida.El power clutch ring E or sleeve is provided with a square groove in its center to accommodate the loader fork, through which it moves forward and backward in the shaft, according to one or the other clutch is to be launched into an active position and to be driven around by the strap on the one or the other pulley.
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